“He didn’t like people coming into the studio and seeing the paintings before they were finished,” he said. “This is one of the most ambitious artworks ever envisioned, certainly in the United States.”

Heizer's mammoth masterpiece in the desert is called "City."

“It was in 1994 when I first saw it, unfinished,” Govan said. “You do cry. You think, what an incredibly beautiful ambition.”
— ksl.com

The giant mall you see in the photos here didn’t die. It has never lived, having been nothing but empty since it opened seven years ago. According to its Wikipedia entry, it has an astounding 2,350 available retail spaces, only 47 of which are occupied.

Meet the world’s largest shopping mall, the New South China Mall in Dongguan, China. It is twice as big as the huge Mall of America outside Minneapolis.
— thinkprogress.org

On Wednesday Lord Foster announced a plan so big that even Burnham would have been impressed. The Thames Hub, a £50bn project devised by architects Foster and Partners, planners and builders Halcrow and Volterra, a consultancy group of British economists, aims to revolutionise Britain's often creaking and largely inadequate national transport and energy infrastructure.
— guardian.co.uk